Single-step conversion of levulinic acid to valeric acid over bimetallic Ni-Co/H-ZSM-5 catalysts

Single-step conversion of levulinic acid (LA) to valeric biofuel is extremely promising for the development of bio-refineries. Direct conversion of LA to valeric acid (VA) was investigated over H-ZSM-5 supported Ni, Co, and Ni-Co (different Ni/Co wt. % ratios) catalysts under ambient reaction conditions (543 K and atmospheric pressure) in the gas phase. Compared with supported monometallic catalysts, bimetallic Ni-Co catalysts exhibited more activity and selectivity toward VA production. Among Ni-Co/H-ZSM-5 catalysts, 15Ni-5Co/H-ZSM-5 catalyst is optimum with 97.5 % conversion of LA and 63 % selectivity to valeric acid even after 6 h time-on-stream (TOS). The active metallic sites are responsible for the hydrogenation of LA to gamma-valerolactone (GVL), and acidic sites catalyze the conversion of GVL to VA. All the catalysts were characterized using the XRD, H-2-TPR, N-2-adsorption-desorption isotherms, NH3-TPD, Py-IR, SEM, HR-TEM and XPS techniques.